JP2009222507A - Trace material detection element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a trace material with high sensitivity, by further improving the performance of an element used for detecting the trace material with high sensitivity, by using localized plasmon resonance. <P>SOLUTION: This trace material detection element utilizing plasmon resonance has a substrate; a plurality of fine projection parts or fine pores formed on one surface of the substrate; and a metal layer formed on the upper surface of the projection parts and on the substrate surface, or a metal layer formed on a peripheral part and the bottom surface of the fine pores. In the trace material detection element, the metal layer formed on the upper surface of the projection parts is in a noncontact state with the metal layer formed on the substrate surface, or the metal layer formed on the peripheral part of the fine pores is in a noncontact state, with the metal layer being formed on the bottom surface of the fine pores. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an element for detecting trace substances with high sensitivity using localized plasmon resonance and a method for manufacturing the same.

  Surface plasmon resonance is generated by resonance of free electron density waves on the metal surface, that is, surface plasmon wave and evanescent wave caused by incident light when light is incident on the metal surface. Depending on the refractive index of the metal surface medium, etc., the resonance conditions change sensitively using them as parameters. Therefore, by monitoring the intensity of the reflected light, it is possible to analyze the state change of the substance on the metal surface.

  As a method for causing surface plasmon resonance, there are a prism optical system and a diffraction grating optical system. The former is based on simple total reflection, and has the disadvantages that the energy of the plasmon resonance field is very small and that there is no degree of freedom in the incident angle that satisfies the resonance condition. On the other hand, the diffraction grating optical system (see Patent Document 1 and Patent Document 2 below) is effective in terms of increasing the intensity of the resonance field, but restricts the conditions for coupling the excitation light to the diffraction grating as in the prism optical system. Therefore, there is a problem that it is extremely difficult to manufacture a diffraction grating.

  On the other hand, a method of detecting a substance present in the vicinity of a metal with high sensitivity by using localized plasmon resonance induced by irradiating excitation light to metal fine particles or metal nanostructures arranged on a substrate. It has been known. For example, using an anodized alumina substrate in which micropores are formed, gold is disposed discontinuously in each of the micropores and around the micropores, and gold fine particles in the pores and a gold thin film around the pores There is known a method for detecting a trace substance using a localized plasmon resonance field generated by each of the above (see Patent Document 3 below).

  In addition, the gap between isolated metal nanodots arranged two-dimensionally on the substrate surface is controlled at the nano level, and using the localized plasmon resonance field generated in the gap, ecological substances such as nucleic acids, sugar chains, proteins, etc. There is also a proposal that non-ecological substances such as PCB and dioxin can be detected (for example, see Patent Document 4 below).

However, when an anodized alumina substrate is used, it is difficult to control the shape and arrangement period of the micropores, and it is also difficult to integrate a substance to be measured introduction / discharge system and an excitation light incident optical system. In addition, when using isolated metal nanodots arranged two-dimensionally, there is a limit to increasing the area in terms of strictly controlling the gap distance at the nano level.
Patent 1903195 Patent 2502222 JP 2004-232027 A JP 2007-218900 A

  The present invention has been made in view of the above-described problems of the prior art, and the main purpose of the present invention is to improve the performance of an element used to detect trace substances with high sensitivity using localized plasmon resonance. Further improvement is to enable trace substances to be measured with high sensitivity.

  The inventor has conducted extensive research to achieve the above-described object. As a result, when a plurality of microprojections or micropores are formed on the substrate, and a metal layer is formed in a non-contact state on the top surface and substrate surface of the projections, or on the periphery and bottom surface of the micropores. It has been found that an electric field is generated in the gap between the metal layers during light irradiation, and by adjusting the size of the gap, the strength of the electric field can be greatly improved and trace substances can be measured with high sensitivity. . In addition, as a method of manufacturing an element having such a structure, after a layer having a high etching rate and a slow layer with respect to wet etching are sequentially stacked on a substrate, microprojections or micropores are formed in the stacked portion, and then wet processing is performed. It has been found that by etching, a portion where etching has progressed can be formed in an intermediate portion between the upper surface of the protrusion and the substrate surface, or an intermediate portion between the surface and the bottom surface of the fine hole. And when forming a metal layer by a vapor phase method with respect to the board | substrate with which the projection part or the micropore was partially etched in this way, precipitation of a metal layer is prevented in the etched part, It was found that the element for detecting a trace substance having the above structure can be manufactured by a simple method. The present invention has been completed as a result of further research based on these findings.

That is, the present invention provides the following element for detecting a trace substance and a method for producing the element.
1. An element for detecting a trace substance using plasmon resonance having a substrate, a plurality of minute protrusions formed on one surface of the substrate, and a metal layer formed on the upper surface and the substrate surface of the protrusion,
An element for detecting a trace substance, wherein a metal layer formed on an upper surface of the protrusion and a metal layer formed on a substrate surface are in a non-contact state.
2. Item 2. The trace substance detection element according to Item 1, wherein the protrusion includes at least one portion having a diameter smaller than that of the upper surface of the protrusion.
3. Item 3. The trace substance detection element according to Item 1 or 2, wherein the distance between the shortest portion of the metal layer formed on the upper surface of the protrusion and the metal layer formed on the substrate surface is 5 nm to 10 μm.
4). A trace substance detection element using plasmon resonance having a substrate, a plurality of micro holes formed on one surface of the substrate, and a metal layer formed on a peripheral portion of the micro holes and a bottom surface of the micro holes,
An element for detecting a trace substance, wherein a metal layer formed in a peripheral portion of the micropore and a metal layer formed on a bottom surface are in a non-contact state.
5. Item 5. The trace substance detection element according to Item 4, wherein at least one portion having a pore diameter larger than the surface of the micropore is present in the micropore.
6). Item 6. The trace substance detection element according to Item 4 or 5, wherein the distance between the shortest portion of the metal layer formed in the peripheral part of the microhole and the metal layer formed on the bottom surface of the microhole is 5 nm to 10 μm.
7). Item 7. The trace substance detection element according to any one of Items 1 to 6, wherein the metal layer is composed of gold, silver, copper, or a mixture containing these.
8). The manufacturing method of the element for a trace substance detection in any one of said claim | item 1-7 which consists of the following processes:
(1) forming at least two layers having different etching rates by wet etching on a substrate such that a layer having a high etching rate is close to the substrate surface;
(2) a step of dry-etching the layer formed on the substrate in the step (1) to form a minute protrusion or a minute hole;
(3) A step of subjecting the substrate on which the fine protrusions or fine holes are formed in the step (2) to wet etching,
(4) A step of forming a metal layer by a vapor deposition method or a sputtering method on the substrate subjected to the etching process in the step (3).
9. The substrate is a silica glass plate or a silicon plate, and at least one of the layers formed on the substrate is a layer made of silica glass or a layer made of silica glass containing fluorine, and wet etching is performed with a hydrofluoric acid aqueous solution. Item 9. The method according to Item 8.

Hereinafter, first, a method for producing a trace substance detection element of the present invention will be described, and then the structure of the element will be described.
(1) Manufacturing method of trace substance detection element :
(I) In the present invention, first, at least two layers having different etching rates for wet etching are formed on a substrate. At this time, each layer is formed so that the layer having a high etching rate is located close to the substrate surface. FIG. 1 is a schematic view showing a state in which a first layer 2 having a high etching rate and a second layer 3 having a low etching rate compared to the first layer are laminated on a substrate 1.

  The substrate 1 is not particularly limited, and can be used without any particular limitation as long as it does not change in the manufacturing process described later and is not affected by a solution containing a trace substance to be measured. For example, silicon, glass, various resins and the like that are easily available as commercial products can be used. In consideration of known photolithography, electron beam lithography, patterning by imprinting, and subsequent dry etching or wet etching processes, the substrate preferably has an optically flat surface.

  The type of layer formed on the substrate is not particularly limited, and a material having an appropriate workability in a process for forming a microprojection or microhole described later and a process for adjusting the cross-sectional shape of the microprojection or microhole by wet etching. You can choose from.

  For example, when silica glass or a silicon plate is used as the substrate 1, the first layer 2 made of silica glass containing fluorine is formed on the substrate, and the silica glass layer is formed as the second layer 3 on the first layer 2. The etching rate of the first layer 2 can be easily controlled by adjusting the fluorine content of the first layer 2.

When silicon is used as the substrate 1, the SiO ₂ layer is formed as the first layer 2 on the substrate, and the silicon layer is formed as the second layer 3 on the substrate, thereby giving priority to the etching of the SiO ₂ layer. Can be advanced. In this case, if fluorine atoms are added to the first SiO ₂ layer, the etching rate of the first layer 2 can be further adjusted.

  The thicknesses of the layers 2 and 3 formed on the substrate 1 are not particularly limited, but an appropriate film thickness may be determined according to the shape of the protrusions or fine holes in the final target element.

  In the present invention, the number of layers formed on the substrate is not limited to two, and three or more layers having different etching rates may be stacked. Also in this case, it is only necessary to have a portion in which a layer having a high etching rate and a layer having a low etching rate are laminated so that the layer having a high etching rate is close to the substrate surface.

  The method for forming each layer is not particularly limited, and for example, various gas phase methods such as CVD, vapor deposition, and sputtering, and wet coating methods such as spin coating can be applied.

  (Ii) Next, a plurality of microprojections or micropores are formed by dry etching on the layer formed on the substrate by the method described above.

  The size of the microprojections or micropores is not particularly limited, but it is possible to obtain high electric field strength by forming the projections or micropores as densely as possible. In consideration of processability, usually, the diameter of the protrusion or the diameter of the fine hole is preferably about 20 nm to 100 μm, and more preferably about 50 nm to 10 μm. In addition, the shortest distance between adjacent protrusions or micropores is usually about 5 nm to 500 nm, preferably about 10 nm to 200 nm.

  In addition, there is no limitation in particular about the cross-sectional shape of a protrusion part and a micropore in the direction parallel to a substrate surface, A perfect circle may be sufficient or a polygon may be sufficient. In this case, the diameter of the protrusion or the hole diameter of the micro hole means the maximum length of the cross section parallel to the substrate with respect to the protrusion or the micro hole.

  Further, the upper surface of the protruding portion may not be a complete flat surface, and may be in a curved surface state by wet etching described later. Similarly, the bottom surface of the fine hole may not be a perfect plane and may be in a curved surface state.

  The above-described protrusions or fine holes can be easily formed by using a well-known patterning technique and etching technique. For example, first, after spin-coating a photoresist on the substrate surface, for example, by irradiating with an interference fringe using a He—Cd laser beam having a wavelength of 325 nm for a predetermined time, and developing, a predetermined pattern of openings is formed. A photoresist layer can be formed.

  FIG. 2 is a schematic view showing a state in which a photoresist layer for forming fine holes is formed. A first layer 2 and a second layer 3 are laminated on a substrate 1, and a resist layer 4 having openings 5 having a predetermined pattern is formed thereon.

  FIG. 3 is a schematic view showing a state in which a photoresist layer for forming the minute protrusions is formed. A first layer 2 and a second layer 3 are laminated on a substrate 1, and a resist layer 6 having a pattern that matches the cross-sectional shape of the protrusions formed thereon is formed.

Thereafter, for example, by performing plasma etching using a fluorine-based gas such as H ₃ F ₈ or CHF ₃ , a chlorine-based gas such as Cl _2, or the like, a protrusion having a desired size, period, or fineness is formed on the substrate. A hole can be formed. Further, even when electron beam drawing and dry etching are performed after the electron beam resist is coated, projections or fine holes having the same shape can be formed.

  FIG. 4 is a cross-sectional view schematically showing a state in which fine holes are formed on one surface of the substrate 1. In FIG. 4, fine holes reaching the surface of the substrate 1 in a state of penetrating the first layer 2 and the second layer 3 are formed.

  About the height of the projection part formed, or the depth of a micropore, it can adjust easily by setting etching conditions appropriately. As will be described later, in the trace substance detection element using the localized plasmon resonance which is an object of the present invention, the distance between the shortest portions between the metal layers is about 5 nm to 10 μm in order to improve the electric field strength of the localized plasmon resonance. It is preferable that it exists in the range. For this reason, about the height of a projection part or the depth of a micropore, according to the thickness of the metal layer formed by the method mentioned later, the space | interval of the shortest part between metal layers after forming a metal layer is 5 nm- It is preferable to adjust so as to be about 10 μm, preferably about 20 nm to 2 μm. However, in consideration of the difficulty of production, the height of the protrusions or the depth of the fine holes is preferably about 50 nm to 2 μm. When the height of the protrusions or the depth of the fine holes is smaller than the above range, it becomes difficult to control the film thickness during metal film formation. If the above range is exceeded, there is a limit to the etching rate difference between the substrate and the resist at the time of etching, so it is necessary to use a metal-based material other than the resist, for example, chromium, nickel, tangle suicide as a mask, Furthermore, there is a problem that the time for forming the subsequent metal layer becomes long.

  (Iii) Next, the substrate on which the fine protrusions or fine holes are formed by the above-described method is subjected to wet etching. Thereby, when the protrusion is formed, the etching of the second layer 2 having a high etching rate proceeds on the side wall portion of the protrusion, and a portion having a smaller diameter than the upper surface of the protrusion is formed. It is formed. In addition, in the case where micropores are formed, the etching of the second layer 2 having a high etching rate proceeds in the side wall portion of the micropore, and the portion having a larger pore diameter than the surface portion has a micropore. Formed inside.

  FIG. 5 is a plan view and a cross-sectional view schematically showing a state after wet etching is performed on a substrate on which a plurality of fine holes are formed. In FIG. 5, in the fine holes penetrating the first layer 2 and the second layer 3 formed on the substrate 1, the etching of the second layer 2, which has a high etching rate, proceeds, and the fineness of the portion of the second layer 2 The hole diameter of the hole is larger than the hole diameter of the surface portion.

  FIG. 6 is a plan view and a cross-sectional view schematically showing a state after wet etching is performed on a substrate on which a plurality of minute protrusions are formed. In the minute protrusion formed in the portion where the first layer 2 and the second layer 3 are laminated, the etching of the first layer 2 having a high etching rate proceeds, and the diameter of this portion is the upper surface portion of the protrusion. It is smaller than the diameter.

  The degree of etching of the microprojection or the side wall portion of the microhole is not particularly limited. In the metal layer formation step by the vapor phase method described later, metal adhesion to the side wall is prevented, and the top surface of the projection is formed. The side wall portion of the protrusion or the metal layer formed on the substrate surface or the metal layer formed on the periphery of the fine hole and the metal layer formed on the bottom surface can be prevented from contacting each other. It is only necessary that the side wall portion of the fine hole is etched.

  The erosion state of the etched part may not be uniform over the entire side wall part, and only a part of the side wall may be etched. Alternatively, the side wall portion may be etched in various shapes such as a stepped shape and a curved shape. Such a non-uniform etching state of the side wall is, for example, when the fluorine-added silica glass layer is formed by a method to be described later, and the fluorine addition amount is changed partially or in the gradient direction in the thickness direction of the silica glass layer. Thus, it can be easily formed by adjusting the etching rate.

  There is no particular limitation on the wet etching method, and the etching solution and the etching conditions are set so that the etching of the first layer 2 proceeds preferentially according to the type of material forming the first layer 2 and the second layer 3. Should be adopted.

  For example, when silica glass is used as the substrate 1, the first layer 2 is formed of fluorine-added silica glass, and the second layer (surface layer) 3 is formed of silica glass, etching is performed using a hydrofluoric acid aqueous solution. Thus, the etching of the fluorine-added silica glass layer of the first layer 2 can be preferentially advanced.

  It is well known that when fluorine is added to silica glass, the etching rate of the resulting glass for hydrofluoric acid increases with the amount of fluorine added (reference: Antireflection microstructures fabricated upon fluorine-doped SiO2 films. Opt. Lett., 26, 1642-1644, 2001. K. Kintaka, J. Nishii, A. Mizutani, H. Kikuta, H. Nakano.). Such glass can be easily produced by a chemical vapor deposition method. The amount of fluorine added may be about 0.5 to 10 mol%, preferably about 1 to 6 mol%, based on the entire silica glass. If the amount of fluorine added is less than the above lower limit, the etching rate difference from the silica glass as the surface layer may be too small during subsequent etching with hydrofluoric acid, and if more than the upper limit, The difference in expansion coefficient from silica glass increases, and the substrate may be warped.

  Further, when the second layer 3 forming the uppermost surface is formed of a material that is difficult to be etched with hydrofluoric acid such as silicon, the first layer 2 can be formed of silica glass to which no fluorine is added. Also in this case, by using a hydrofluoric acid aqueous solution as an etchant, it is possible to preferentially advance the etching of the silica glass layer as compared with the silicon layer.

  As described above, when the first layer 2 is formed of fluorine-added silica glass or pure silica glass, an aqueous hydrofluoric acid solution can be used as an etching solution. About the density | concentration of hydrofluoric acid aqueous solution, although it is dependent also on the addition amount of the fluorine in a silica glass, what is necessary is just about 0.1 to 10 weight% normally. The etching rate can be controlled by the concentration of the aqueous solution and the solution temperature. Preferable etching conditions are a temperature of about 15 to 25 ° C. and a time of about 5 seconds to 10 minutes.

  (Iv) After wet etching is performed by the above-described method, a metal layer is formed on the upper surface and substrate surface of the microprojection portion, or on the peripheral portion of the microhole and the bottom surface of the microhole in which the microhole is formed.

  The metal layer is preferably formed, for example, by a vapor phase method such as a vacuum evaporation method or a sputtering method. As a result, a metal layer is formed on the top surface and substrate surface of the microprojection, or on the periphery and bottom surface of the micropore, and the portion corresponding to the second layer 2 is etched on the side wall of the microprojection or the micropore. This prevents the metal from adhering to this portion. As a result, the metal layer formed on the top surface of the microprojection and the metal layer formed on the substrate surface, or the metal layer on the periphery of the microhole and the metal layer formed on the bottom surface of the microhole are not in contact with each other. It becomes.

  FIG. 7 is a cross-sectional view schematically showing a state in which a metal layer is formed on a substrate in which fine holes are formed. In FIG. 7, metal layers 7 and 8 are formed on the periphery of the microhole and on the bottom surface of the microhole, and both are in a non-contact state. FIG. 8 is a cross-sectional view schematically showing a state in which a metal layer is formed on a substrate on which minute protrusions are formed. In FIG. 8, metal layers 9 and 10 are formed on the top surface and the substrate surface of the fine protrusions, and both are in a non-contact state.

  The type of the metal layer is not particularly limited as long as a strong plasmon resonance field can be obtained by light irradiation. For example, gold, silver, copper, a mixture thereof, or the like can be used.

  Regarding the thickness of the metal layer, the metal layer formed on the upper surface of the protrusion and the metal layer formed on the substrate surface according to the height of the protrusion formed on the substrate or the depth of the fine hole, Or the distance between the shortest portion between the metal layer formed at the periphery of the micropore and the metal layer formed at the bottom surface of the micropore is about 5 nm to 10 μm, preferably 20 nm to It is preferable to adjust so that it may become about 2 micrometers.

  By setting the distance between the shortest portions of the metal layers within the above range, the intensity of the electric field generated between the metal layers when irradiating light during detection measurement is remarkably enhanced, and both of the metal layers formed with a gap are provided. The enhanced signal can be observed simultaneously, and trace substances can be detected with high sensitivity. By adopting a vapor phase method such as a vacuum deposition method or a sputtering method, the film thickness of the formed metal layer can be easily controlled.

  In this case, the distance between the shortest portions between the metal layers is, for example, when the metal layer is formed on the upper surface of the protrusion and the substrate surface, the edge portion on the lower surface of the metal layer formed on the upper surface of the protrusion, and the substrate When the edge portion on the upper surface of the metal layer formed on the surface is the shortest distance, the interval between these edge portions is referred to.

  The film thickness of the metal layer may be any thickness that generates plasmons by light irradiation. For example, plasmon resonance can be obtained when the thickness is about 10 nm or more.

(2) Trace element detection element structure :
According to the method described above, the substrate has a plurality of minute protrusions formed on one surface of the substrate, the upper surface of the protrusion and the metal layer formed on the substrate surface, and the upper surface of the protrusion. A trace substance detecting element utilizing plasmon resonance in which the metal layer formed on the substrate and the metal layer formed on the substrate surface are in a non-contact state, or
A substrate, a plurality of micropores formed on one surface of the substrate, a metal layer formed on a peripheral portion and a bottom surface of the micropore, and a metal layer formed on the peripheral portion of the micropore, A trace substance detection element using plasmon resonance in which the metal layer formed on the bottom surface is in a non-contact state can be obtained.

  Among these elements for detecting a trace substance, in an element in which a minute protrusion is formed, the protrusion has at least one portion having a smaller diameter than the upper surface of the protrusion. Further, in an element in which a microhole is formed on the substrate surface, at least one portion having a hole diameter larger than the surface of the microhole is present in the microhole. Such an element is an element having a novel structure that has not been conventionally known.

  In the element of the present invention having the above structure, a metal layer is formed on the upper surface and the substrate surface of the protrusion for the element having the protrusion, and a metal layer is formed on the peripheral and bottom surfaces of the hole for the element having the minute hole. The formed plasmon resonance field generated by light irradiation is localized at the edge portions of these metal layers. Then, the shortest distance between the metal layers formed on the top surface of the microprojection part and the substrate surface, or the shortest distance between the metal layers formed on the peripheral part and bottom surface of the microhole is set to a predetermined range, particularly about 5 nm to 10 μm. By adjusting, the electric field strength of the localized plasmon resonance field can be remarkably improved.

  The gap between the metal layers formed on the upper surface and the substrate surface of such a protrusion or the gap between the metal layers formed on the periphery and the bottom surface of the fine hole, that is, the gap between the metal layers in the height direction is adjusted. Thus, the element for measuring a trace substance with improved electric field strength of the localized plasmon resonance field is an element having a novel structure that has not been known at all.

According to the calculation result by the time domain difference method, the element for measuring a trace substance of the present invention having the above-described characteristics has an electric field strength of 10 ⁵ times that of a plasmon resonance field generated on a flat metal surface. It is strengthened to the above. Therefore, by using the trace substance detection element of the present invention, it is possible not only to detect a conventional trace substance having a concentration of 10 ⁻⁵ or less with high sensitivity, but also to integrate it into other analysis devices such as micro-flow dew.

  As described above, the trace substance detection element of the present invention is a detection element used in a sensor that utilizes localized plasmon resonance, and has a novel structure that has not existed in the past, and an electric field of a localized plasmon resonance field. The strength is improved, and trace substances can be detected with high sensitivity.

  In addition, according to the method for manufacturing a trace substance detection element of the present invention, the detection element having the above-described novel structure is accurately manufactured by a relatively simple manufacturing method using a vapor phase method and wet etching. be able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the following examples, a case where silicon or silica glass is used as a substrate, fluorine-added silica glass is formed as an intermediate layer on the surface, and silica glass is formed as an outermost layer will be described. The trace substance detection element according to the present invention is not limited to the following form. For example, silicon / silica glass / silicon, silicon / silica glass / silicon nitride, silicon / silica glass, silicon / silica glass / silicon nitride, It can manufacture by applying the method of the following Example using the board | substrate which laminated | stacked the layer of various combinations, such as resin / silica glass and resin / silica glass / resin.

Example 1
Example 1 shows an example in which a trace substance detection element is manufactured using a substrate in which a plurality of fine holes are formed. The micropores formed on the substrate have a pore diameter of 150 nm, a depth of 100 nm, and an interval between adjacent micropores of 300 nm. An element having such a shape can be manufactured with good reproducibility through the following steps. Note that the manufacturing conditions described below are typical examples of the apparatus used in the present invention, and do not limit the present invention.

(1) An optically polished silicon plate was used as the substrate, and a fluorine-added silica glass film having a thickness of 50 nm was formed on the surface of the silicon plate by plasma CVD. C ₂ F ₆ gas was used as the fluorine raw material, and tetraethoxysilane was used as the silica raw material, and these raw materials were decomposed in oxygen plasma and deposited on the substrate.

(2) Next, C ₂ F ₆ gas as a fluorine raw material was stopped, and a pure silica glass layer was continuously deposited to 50 nm. When the refractive index of the obtained glass layer was measured by ellipsometry, it was 1.42 for the fluorine-added silica glass film and 1.47 for the silica glass layer, and it was confirmed that the refractive index was lowered by fluorine addition. . Moreover, when the fluorine content of the former was measured by ESCA, it was about 6 mol%.

  FIG. 1 is a schematic view showing a state in which a fluorine-containing silica glass film and a silica glass film are laminated on a silicon substrate.

(3) The silica glass film obtained in the step (2) is spin-coated with an i-line resist so as to have a film thickness of 400 nm, and interference light of a He—Cd laser (about 200 μW / cm ² ) having a wavelength of 325 nm is applied. Irradiated for 90 seconds. Thereafter, the shutter was temporarily closed, the substrate was rotated 90 degrees, and irradiation was performed again at the same time. After the irradiation, development was performed for 3 minutes to obtain a desired resist pattern. FIG. 2 is a schematic view showing a state in which a resist pattern film after development is formed.

(4) Next, the glass layer formed in the steps (1) and (2) was dry-etched through a resist mask. As dry etching conditions, a high frequency induction plasma power of 200 W, a bias high frequency power of 100 W, a chamber pressure of 1 Pa, Ar: 70 cc / min, and C ₃ F ₈ : 30 cc / min were introduced as etching gases. The substrate temperature during etching was set to 5 ° C., and a cycle of 10-minute etching and 60-second cooling was repeated a plurality of times.

  (5) Next, ashing was performed for about 10 minutes in oxygen plasma (power 300 W, pressure 100 Pa) without applying a bias, and the resist remaining on the surface was removed. FIG. 4 is a cross-sectional view schematically showing a structure in which fine holes after dry etching are formed.

  (6) The obtained structure was immersed in a 0.5% hydrofluoric acid aqueous solution kept at 20 ° C. for 10 seconds, and then quickly washed with distilled water, and the fluorine-containing silica with fine pore side walls as shown in FIG. A structure in which the glass film portion was wet-etched was formed.

  (7) Next, a 40 nm gold film was formed on the etched substrate surface by sputtering. The film forming conditions are as follows. FIG. 7 is a cross-sectional view schematically showing the structure after gold film formation.

Target gold (2 inches φ)
Substrate temperature Room temperature Target-substrate distance 150mm
Substrate rotation None Introduced gas Argon 50 cc / min Pressure during film formation 4 Pa
Deposition time 4 minutes (8) The structure obtained by depositing gold by the method described above was placed in the optical system shown in FIG. 9, and a concentration of 10 ⁻⁸ mol / liter was placed in the gap between the substrate and the objective lens. A pyridine solution was added dropwise, and a Raman scattering spectrum using a laser having a wavelength of 785 nm as excitation light was measured. As a result, as shown in FIG. 10, a peak derived from the pyridine skeleton was detected at a wave number of 1023 cm ⁻¹ .

Example 2
Example 2 shows an example in which a trace substance detection element is manufactured using a substrate on which a plurality of minute protrusions are formed. The protrusions formed on the substrate have a diameter of 150 nm, a height of 100 nm, and an interval between adjacent protrusions of 300 nm. An element having such a shape can be manufactured with good reproducibility through the following steps. Note that the manufacturing conditions described below are typical examples of the apparatus used in the present invention, and do not limit the present invention.

(1) After laminating a fluorine-containing silica glass film and a silica glass film on a silicon substrate in the same manner as in Example 1, an i-line resist was spin-coated to a film thickness of 400 nm, and He—Cd having a wavelength of 325 nm. Laser interference light (about 200 μW / cm ² ) was irradiated for 120 seconds. Thereafter, the shutter was temporarily closed, the substrate was rotated 90 degrees, and irradiation was performed again at the same time. After the irradiation, development was performed for 3 minutes to obtain a desired resist pattern. FIG. 3 is a schematic view showing a state in which a resist pattern after development is formed.

(2) Next, the fluorine-containing silica glass film and the silica glass film were dry-etched through a resist mask. As dry etching conditions, a high frequency induction plasma power of 200 W, a bias high frequency power of 100 W, a chamber pressure of 1 Pa, Ar: 70 cc / min, and C ₃ F ₈ : 30 cc / min were introduced as etching gases. The substrate temperature during etching was set to 5 ° C., and a cycle of 10-minute etching and 60-second cooling was repeated a plurality of times.

  (3) Next, in the same manner as in Example 1, oxygen plasma ashing and hydrofluoric acid etching were performed to form a structure in which the fluorine-containing silica glass film on the side walls of the protrusions was etched as shown in FIG.

  (4) Next, a 40 nm gold film was formed on the etched substrate surface by sputtering. The film forming conditions are the same as in Example 1. FIG. 8 is a cross-sectional view schematically showing the structure after gold film formation.

(5) The structure obtained by depositing gold by the above method is placed in the same optical system as in Example 1, and a pyridine solution having a concentration of 10 ⁻⁸ mol / liter is placed in the gap between the substrate and the objective lens. Was dropped, and a Raman scattering spectrum using a laser having a wavelength of 785 nm as excitation light was measured. As a result, as shown in FIG. 11, a peak derived from the pyridine skeleton was detected at a wave number of 1023 cm ⁻¹ .

Comparative Example 1
A 40 nm thick gold film was formed on the optically polished silicon substrate by the same method as in step (7) in Example 1. Next, a silicon substrate on which gold was formed was placed in the same optical system as in Example 1. A pyridine solution having a concentration of 10 ⁻⁸ mol / liter was dropped into the gap between the substrate and the objective lens, and a laser with a wavelength of 785 nm was applied. When a Raman scattering spectroscopic spectrum as excitation light was measured, no peak derived from the pyridine skeleton could be detected.

  Further, a 12 mol / liter pyridine solution was measured by the same method, and as shown in FIG. 12, a peak was detected at the same wave number position as in Examples 1 and 2.

From the above results, the devices obtained in Examples 1 and 2 were able to detect pyridine in a pyridine solution having a low concentration of 10 ⁻⁸ mol / liter, whereas those obtained in Comparative Example 1 were obtained. It can be seen that the device cannot detect such a low concentration of pyridine.

Schematic which shows the state which laminated | stacked the layer with a quick etching rate, and the layer with a slow etching rate on the board | substrate. Schematic which shows the state in which the photoresist layer for forming a micropore was formed. Schematic which shows the state in which the photoresist layer for forming a microprotrusion part was formed. Sectional drawing which shows typically the state by which the fine hole was formed in the one surface of a board | substrate. The top view and sectional drawing which show typically the state after performing wet etching with respect to the board | substrate with which the several fine hole was formed. The top view and sectional drawing which show typically the state after performing wet etching with respect to the board | substrate with which the several microprotrusion part was formed. Sectional drawing which shows typically the state which formed the metal layer in the board | substrate with which the fine hole was formed. Sectional drawing which shows typically the state which formed the metal layer in the board | substrate with which the microprotrusion part was formed. 1 is a schematic diagram of an optical system for Raman scattering spectrum measurement used in Example 1. FIG. FIG. 3 shows a Raman scattering spectrum measured in Example 1. FIG. FIG. 3 is a drawing showing a Raman scattering spectrum measured in Example 2. FIG. The figure which shows the Raman scattering spectrum detected in the pyridine solution of the density | concentration of 12 mol / liter measured in the comparative example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Layer with high etching rate 3 Layer with low etching rate 4 Resist layer 5 Resist layer opening 6 Resist layer 7, 8, 9, 10 Metal layer

Claims (9)

An element for detecting a trace substance using plasmon resonance having a substrate, a plurality of minute protrusions formed on one surface of the substrate, and a metal layer formed on the upper surface and the substrate surface of the protrusion,
An element for detecting a trace substance, wherein a metal layer formed on an upper surface of the protrusion and a metal layer formed on a substrate surface are in a non-contact state. The trace substance detection element according to claim 1, wherein the protrusion includes at least one portion having a diameter smaller than that of the upper surface of the protrusion. The element for detecting a trace substance according to claim 1 or 2, wherein a distance between a shortest portion between the metal layer formed on the upper surface of the protrusion and the metal layer formed on the substrate surface is 5 nm to 10 µm. A trace substance detection element using plasmon resonance having a substrate, a plurality of micro holes formed on one surface of the substrate, and a metal layer formed on a peripheral portion of the micro holes and a bottom surface of the micro holes,
An element for detecting a trace substance, wherein a metal layer formed in a peripheral portion of the micropore and a metal layer formed on a bottom surface are in a non-contact state. The element for detecting a trace substance according to claim 4, wherein at least one portion having a hole diameter larger than that of the surface of the fine hole is present in the fine hole. The element for detecting a trace substance according to claim 4 or 5, wherein a distance between a shortest portion of the metal layer formed in the peripheral portion of the fine hole and the metal layer formed on the bottom surface of the fine hole is 5 nm to 10 µm. The element for detecting a trace substance according to any one of claims 1 to 6, wherein the metal layer is made of gold, silver, copper, or a mixture containing these. The manufacturing method of the element for a trace substance detection in any one of Claims 1-7 which consists of the following processes:
(1) forming at least two layers having different etching rates by wet etching on a substrate such that a layer having a high etching rate is close to the substrate surface;
(2) a step of dry-etching the layer formed on the substrate in the step (1) to form a minute protrusion or a minute hole;
(3) A step of subjecting the substrate on which the fine protrusions or fine holes are formed in the step (2) to wet etching,
(4) A step of forming a metal layer by a vapor deposition method or a sputtering method on the substrate subjected to the etching process in the step (3). The substrate is a silica glass plate or a silicon plate, and at least one of the layers formed on the substrate is a layer made of silica glass or a layer made of silica glass containing fluorine, and wet etching is performed with a hydrofluoric acid aqueous solution. The method of claim 8.

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